From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A696ECDFB0 for ; Fri, 13 Jul 2018 02:23:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3C5A7214AB for ; Fri, 13 Jul 2018 02:23:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3C5A7214AB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388097AbeGMCf2 (ORCPT ); Thu, 12 Jul 2018 22:35:28 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:35249 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388021AbeGMCf2 (ORCPT ); Thu, 12 Jul 2018 22:35:28 -0400 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 221167D74C13E; Fri, 13 Jul 2018 10:22:59 +0800 (CST) Received: from [127.0.0.1] (10.177.223.23) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.382.0; Fri, 13 Jul 2018 10:22:53 +0800 Subject: Re: [PATCH 1/1] iommu/arm-smmu-v3: prevent any devices access to memory without registration To: "Leizhen (ThunderTown)" , Will Deacon CC: Jean-Philippe Brucker , Robin Murphy , Joerg Roedel , linux-arm-kernel , iommu , linux-kernel References: <1531387723-3592-1-git-send-email-thunder.leizhen@huawei.com> <20180712170120.GC26935@arm.com> <5B4804D6.4050508@huawei.com> From: Hanjun Guo Message-ID: <8067f5d2-b241-d5f2-42f6-466913f04e04@huawei.com> Date: Fri, 13 Jul 2018 10:22:51 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <5B4804D6.4050508@huawei.com> Content-Type: text/plain; charset="windows-1252" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.223.23] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/7/13 9:48, Leizhen (ThunderTown) wrote: > > > On 2018/7/13 1:01, Will Deacon wrote: >> On Thu, Jul 12, 2018 at 05:28:43PM +0800, Zhen Lei wrote: >>> Stream bypass is not security. A malicious device can be hot plugged >>> without match any drivers, but it can access to any memory. So change to >>> disable bypass by default. >>> >>> Signed-off-by: Zhen Lei >>> --- >>> drivers/iommu/arm-smmu-v3.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> Whilst this sounds nice, I *bet* you it will break some systems. In >> particular, those where the SMMU is described but the toplogical information >> is either incorrect or incomplete. > > Suppose this scene exists, maybe we should consider updating IORT specification, > to indicate whether a smmu treats all unregistered devices as stream bypass or not, --- global control > to indicate whether a single device default use stream bypass or not, --- local control > that will be more flexible. But we still disable bypass by default. IORT (or dts) is about the hardware feature, if it's only about the wrong topological information of devices and SMMU, I think IORT is not the right place to describe such information, we need correct that information instead. Thanks Hanjun